Sewage digester



Sept. 15, 1936- c. E. KEEFER ET AL SEWAGE DIGE STER v 2 Sheets-Sheet l Original Filed June 9, l93l Sept. 15, 193.6. c. E. KEEFER ET AL.

SEWAGE DIGESTER original Filed June 9, '1931 2 Sheets-Shes?l 2 CLARENCE E KEEEER FRA/wr c wAcHE/P Clecamaaavm (bung Patented Sept. 15, 1936 UNITED sTATEs PATENT OFFICE SEWAGE DIGESTER Ware Original application June 9, 1931, Serial No.

Divided and this application November 16, 1931, Serial N0. 575,448

7 Claims.

In the treatment of sewage and the like, the putreacible solids therein are separated therefrom in the form of a sludge, usually by sedimentation means. This sludge, as a step in its treatment to render it inert and odorless, is exposed to anaerobic bacterial action in a digester. This invention relates, among other things. to the construction of such a digester.

Sewage digesters comprise generally a sedimentation tank having driven mechanisms therein for impeiling solids settling in the tank, toa sludge discharge outlet. These mechanisms are sometimes propelled through the medium of a vertical shaft in the digester which extends above the digester cover to be driven by a suitable motor and gearing. A trussed bridge extends across the top of the digester tank for supporting the upper end of the vertical shaft and for supporting the driving motor mechanism.

With the present tendency toward beautifying sewage treating plants, it has become desirable to re-design the digesters and other tanks to eliminate therefrom the present unsightly truss construction. Therefore, one object of this invention is to meet that requirement. y

However, to eliminate the trusses is not as easy as it may appear because it has entailed a redesign and re-arrangement of many of the digester elements. Accordingly, it has been necessary to provide means for supporting the inner edges of a substantially annular top; for instance,

a center pier in the digester arranged to support aframework which, by means. of hangers therefrom, in turn supports the'inner ends of thev digester roof-bearing members whose outer ends are supported by the digester wall.

The invention is broad enough to comprehend other features which comprise an arrangement of sludge-discharging mechanisms to readily conform .to the above described roof design, and which also may comprise a housing for the pier, or extensions thereof, and the motivating elements of the sludge discharge mechanism. This part of the invention is being claimed `separately herefrom.

The invention is illustrated in the accompanying drawings by showing one embodiment of our invention. 'This embodiment is used for illustrative purposes only for obviously many changes and modifications can be made therein without departing from the spirit of our invention as described herein and pointed out in the following claims. 'I'he embodiment chosen for this purpose is a sewage digester but the invention is capable of uses, suchas in claritlers, so the use of the invention is not intended to be limited to any spe: cic eld.

In the drawings, Fig. 1 is a vertical sectional 'view through our sewage digester, with parts broken away.

Fig. 2 is a horizontal sectional view taken along lines II--II in Fig. 1 while Fig. 3 is a vertical sectional view taken along lines III-III in Fig. 1. Fig. 4 is a plan view of the digester with parts broken away. Fig. 5 is a vertical sectional view taken along lines V--V in Fig. 4.

So that the invention may be more clearly understood the partsl shown in the accompanying drawings will be described. The numeral II indicates a sewage digester. I2 indicates the side or boundary walls thereof and I3 its bottom. I4 indicates a sludge discharge hopper, preferably annular in shape having a sludge outlet I5. I6 indicates a shaft, column, or pier upstanding from the digester bottom. In larger sizes of tanks, a concrete pier is preferred but in smaller sizes a metal shaft can be used. The'Y manner of constructing and `supporting the substantially horizontal digester top I'I forms an important part of this invention'so it will now be described. The principle thereof is vto-have either the central pier I6 or anextension thereof, support a framework or spider. Hangers or slings depend from said framework and support inner ends of roof beams, the other ends of which find a bearing upon the digester walls I2. More particularly, the column or pier I6 is provided with an extension I8. In smaller sizes of digesters, the pier or shaft itself can extend above the ldigester top sufliciently to directly support the framework but in the embodiment shown the metal extension I8 is used. This extension is formed of various shaped beams I9, angle bars 20, and braces 2|, as shown in Fig. 2, in any manner which gives the extension I8l sufficient strength. 22 indicates a reinforcing to withstand compressional strains put on the extension as will be described hereinafter. Thetop framework supported by the pier I6, or its extension I8, may be any framework suitable for sustaining the roof-supporting hangers which depend therefrom but in the present embodiment the frame comprises a substantially horizontal plate or cap piece on the extension I8 having a web piece 24 associated therewith. Secured to the web piece 24 are beams 25, and these beams are secured at the outer ends to webs 26. .Stretching between the webs 26 and n plates 21 carried by extension I 8 and radially extending therefrom are compression beams or spreaders 28 top structure such as concrete 34.

while 29 indicate hanger beams or straps or sling members depending from the webs 26 of the top framework, which are arranged to support ,the digester roof. A roof 30 may be provided over the top framework, and a housing 3| or side walls may be provided to enclose the pier extension I8, the top framework to make it more sightly and to protect it from the weather and to forma control house for the digester operating mechanism.

'I'he digester roof is formed of beams 32 preferably radially arranged from the pier I6 having their outer ends resting on the digester boundary wall or walls I2. Adjacent to the inner ends of the said top beams 32, they are secured to the hangers 29 whereby their inner ends may thus be supported.V Some of the top beams 32 or extensions thereof, extend inwardly and terminate adjacent to the pier I6 to form a platform encircling the piery I6 and within the housing 3|. These top beams 32 may have chordal bracing beams 3'! for making the digester top structure more rigid. Over the top beams 32 is placed some Concrete 35 may also be used in the housing 3| to encase the hangers 29 and plates 36 therebetween (Fig. 4). This substantially horizontal digester top may be arranged flush with the surrounding land, as shown in Figure 1, whereby the control house is the only part of the digester observable projecting above the ground.

Having thus described the construction of our digester whereby the use of the usual trusses are eliminated, there will now be described the arrangement of sludge-discharge mechanism adapted to cooperate with the central column or pier, since that pier serves such an important function in our digester tank design.

Solids settled by sedimentation in a digester are usuallyimpelled toward a central annular sludge discharge hopper or outlet, by means of substantially radial arms 40, carrying rakes 4I, presenting a curved face to the sludge. ,In digesters, radial scum-breaking arms 42, may be provided adjacent the top of the digester.

'I'he radial arms 40 and 42, heretofore have been rotated usually by a supporting vertical shaft driven from above the digester.` However, in the present design of digester, it is desired to eliminate the central vertical shaft. In lieu thereof, this invention involves the use of a revoluble drum or sleeve 43 encircling the stationary column or pier I6. The drum may be apertured as at 44, in order to lighten it without sacricing strength and it may be appropriately reinforced either longitudinally as at 53, or annularly, or both, to withstand thrust or compressional tendencies from the rake arms 40.

The drum is hung or depends from a support adjacent its upper end from whence it is driven by a suitable motor and gearing located in juxtaposition'thereto. That is to say, a motor 45, is suitably connected to a speed reducer 46, and drives a gear 41, such as a worm gear, meshing with a cc-acting -bull or ring-gear 48 secured to the drum 43.

This ring-gear 48 isoated upon pier-supported anti-friction bearings, that is, the ring-gear is suitably mounted for rotation upon ballor roller-bearings supported on a casting 50, carried by the pier I6. If the tank be a digester and it is desired to prevent gas from the digester creeping up along the drum 43, one or more wateror oil-seals may be provided such as an inner and outer water seal provided at 5I and 52 respectively.

It will thus be seen that by means of this invention a sewage digester isprovided from which the present unsightly trusses have been eliminated., At the same time this design of covered digester permits its top-supporting center pier or column not only to support the digester roof but to have the further functions of supporting the sludge-discharge mechanism and itsl motor devices which produces an eiiicient digestion apparatus which is not only highly eilicient but reasonable in its cost of construction.

The application upon which this patent is based is a division of an original application filed June 9, 1931 bearing Serial No. 543,131 which matured into patent granted January 3, 1933 and which on March 3, 1936 was reissued as Re. 19,878.

We claim:

1. A sewage digester comprising an enclosing wall, a substantially horizontal annular gas-tight top, beams for sustaining said top supported at the outer ends by said wall, a central pier in said tank, and means associated with and deriving support from said pier and having depending members affording support for the inner ends of said beams.

2. A sewage digester comprising a boundary wall, a bottom, a central pier upstanding from said bottom, a frame element supported from said pier above the tank, a plurality of' tension members depending from said frame, a plurality of beams supported by said boundary wall and secured to one of said tension members, and a substantially horizontal gas-tight top for the tank sustained by said beams.

3. A structure according to claim 2 in which the substantially horizontal top is flush with the surrounding land.

4. Ihe structure according to claim 2 in which said top is annular and encircles said pier, and a control housing adapted toenclose the central opening of said annular top.

5. A .sewage digester comprising a boundary wall, a bottom, a central pier upstanding from said bottom, a raftered frame supported from said pier above said tank, substantially horizontal compression members extending between said frame and said pier, reenforcements embodied in said pier to withstand compression of said pier by said members, sling devices coacting with said frame, beams supported at one end from said sling devices' and at the other end .by said wall, and a substantially horizontal gas-tight, tank top sustained by said beams.

Y 6. The structure according to claim 5 with the addition of chordal braces between said beams.

v'7. A covered tank adapted for use as a sewage digester comprising a boundary wa1l,`a bottom, a substantially horizontal gas-tight top, a single central pier upstanding from said bottom and projecting through saidtop, a spider supported from said pier above said top and means for supporting the central portion of said top from said spider.

CLARENCE E. KEEFER. FRANK C. WACHTER. 

